4K DCI 4096x2560 (16:10)
Digital Cinema Institution official 4K Cinema editing resolution standard; extra vertical pixels are used for toolbars with time stream when editing or viewing edited 4K video. Monitors with this resolution are often referred to as 4K DCI Reference Monitors.

5K 5120x2880 (16:9)
Apple Inc. made this world wide knowledge with the launch of the 2014 iMac with 5K Retina display.

5K 5120x3200 (16:10)
Known as WHXGA, this resolution is designed to support 5K video editing; extra vertical pixels are used for toolbars with time stream when editing or viewing edited 5K video. Monitors with this resolution are often referred to as 5K Reference Monitors.

5K 5120x2160 (21:9)
A standard for film & movie lovers who wish to watch 21:9 cinema scope films on a larger display with support for 4K UHD, 4K DCI & 5K.

Extension on this article will be available as soon as possible, by 1st January 2015, I hope.